"He's been a good friend of hers for over five years," the source shared. "He obviously knows what she went through with Colton and just supported her along the way."
Brighton, 24, reportedly joined Cassie, 26, on her recent vacation to Cozumel, Mexico.
Cassie hopped on a plane for a trip with family and friends after Colton came out as gay April 14 on Good Morning America.
"He gets along very well with her family," the source told Us. "Right now, they're still enjoying spending time with one another and just seeing where things go."
Brighton appeared to take a jab at Colton in his song "Creep" that was released in January.
The song's lyrics include, "You can't stop thinking about my baby / What once was yours in the world is changing / God, I hope you get your thinking right / GPS on the underside / Told her everything will be just fine / Damn, I can't believe these guys."
Brighton was seemingly referring to how Cassie had accused Colton of stalking and harassing her, which resulted in Cassie filing a restraining order against the former NFL player in September 2020 followed by a police report in October.
Colton later told multiple press outlets Cassie ultimately dropped the restraining order after they were able to reach an agreement in private that addressed Cassie's concerns.
Rumors swirled Cassie and Brighton were already dating last summer when fans noticed they were spending time with her family in Huntington Beach, CA, according to Us.
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Not only was it clear Cassie and Brighton had mutual friends, but the pair also noticeably "liked" each other's Instagram content every now and then, dating back to 2019.
Brighton, however, shut down speculation and told the magazine in August 2020 that he and Colton's ex were not dating.
"Cassie and I are just friends and have been for over four or so years," the singer said at the time. "My brothers and I are all close with Cassie and her whole family."
Cassie said in a Youtube video posted to her channel late last month that she's not ready to talk about Colton, although she avoided stating his name and the fact he's gay.
"I just wanted to say thank you all so much for the kind comments and messages from you guys. I really appreciate it. Regarding the topic in the media that brought my name up this week, I just want to let you know that I'm not going to be further discussing it or commenting on it for now," Cassie explained in her video titled "Sneak Peek Into My New Home."
Cassie shared in her vlog, "If I do decide in the future to say anything or make a comment at all, you guys will be the first to know. But I just want to say thank you for now for all the kind messages, comments and DMs."
Cassie explained she's just been "focusing on unpacking and trying to move into [her] new home" and documented herself buying plants and picking out home decor.
Colton and Cassie dated for 18 months after meeting on The Bachelor's 23rd season, which filmed in late 2018, and Colton discussed wanting to propose marriage to her for months.
Although their May 2020 breakup was initially amicable and Colton and Cassie intended on staying friends, Colton appeared to pick a fight with Cassie over an interview she conducted on ABC and then Cassie filed the restraining order because she was reportedly "fearful for her safety."
Cassie had accused Colton of putting a tracking device on her car post-breakup, standing outside of her residence late into the night and sending numerous unwanted text messages.
"It was a very traumatic time for Cassie," the People source said, adding that public interest in Colton's interview about being gay had been a little bit of a struggle for Cassie.
"It's tough to be in the headlines and revisit painful memories."
An insider close to Cassie recently told the UK's Daily Mail that the Randolph family is concerned Colton's alleged alarming behavior last year is being overshadowed and maybe even forgotten by the recent celebration of his coming out.
Reports have even circulated Colton is currently filming a new reality show for Netflix about his journey through life as an openly-gay man. (A Change.org petition has over 35,000 signatures as of May 3 trying to cancel the show due to his past with Cassie).
But the People source said of Cassie, "She is a person of faith and she believes in forgiveness. And ultimately, she's going to be just fine. She's moved on with her life."
In new footage of Colton's GMA interview that aired during the April 15 episode of ABC's Nightline, Colton confirmed he hadn't spoken to Cassie "at all."
"I don't know if I ever will get the chance to sit down and talk with her. I would like to," Colton said.
"I would like to say sorry for how things ended. I messed up. I made a lot of bad choices."
He continued, "I made mistakes at the end of that relationship and I ruined the good memories we had by my actions and what I did to hold on to being straight because I didn't want to look myself in the mirror. So for that, I'm extremely, extremely sorry."
Despite being gay during their near two-year relationship, Colton confirmed he was definitely in love with Cassie, which made acknowledging he's gay and his decision to come out to his family and the public even "harder and more confusing" for him.
"If I'm being very honest, I loved everything about her and it's hard for me to articulate what my emotions were in going through that relationship with her because I obviously had an internal fight going on," Colton explained on GMA.
"I would just say that I'm sorry from the bottom of my heart. I'm sorry for the pain and emotional stress I caused. I wish it wouldn't have happened the way it did."
Colton added, "I wish I would have been courageous enough to fix myself before I broke anybody else."
Colton said he understands why Cassie and his other The Bachelor bachelorettes may feel like he had misled them.
"Do I regret handling [The Bachelor] the way that I did?' I do. I do think I could've handled it better, I'll say that... I just wish I didn't drag people into my own mess of figuring out who I was," Colton admitted.
He added, "I genuinely mean that. But at the same time, I can say 'sorry' to all of those women and also say 'thank you.' Because without them and without The Bachelor franchise, I don't know if I ever would have come out."
Colton said he realized he was different at the age of six and came to the conclusion he was gay in high school. But Colton explained he tried to convince himself he was straight by dating women and starring as the Bachelor.
After "hating" himself "for a long time," Colton revealed he finally accepted his sexuality earlier this year and has never been happier or healthier.
Colton -- who faced rumors he was gay while his The Bachelor season was airing -- said on GMA he's now "proud to be gay" and looking forward to meeting a male partner who can challenge him in new ways.